035_lua快速入门

执行下面的脚本用luajit test.lua即可

一、变量及逻辑运算

--number, string, boolean, table, function, thread, userdata, nil

--<1>Number demo
x = 11 --It's number type,but not an integer
--The two common variable name below in the lua language  is recommended.
exampleVar = 10e5       --equal 1000000
example_var = 666
exampleHexadecimal = 0xFAE  --equal 4014

--<2>String demo
exampleStrings = "Hello 123 &^*& \n"

--nil
print(notDefineVariableIsNil) -- nil

-- MathOperator demo
-- (),a ^b, not a, #a, -a, a*b, a/b, a%b, a+b, a-b, a..b, a<b, a>b(return boolean value), a ~= b(tilde equals !), a == b
-- a and b, a or b
exampleMathModuloOperator = 10/3 --Supporting + - * / %, and so forth.
exampleDecimalRemainder = 10 % 3.3 -- equal 0.1
exponentNum1 = 2
exponentPower = 4
exampleExponentCal = exponentNum1 ^ exponentPower  -- 16
exampleBoolean = true
print(not exampleBoolean) -- false
print(-exponentNum1) -- -2
print( (exponentNum1 + exponentPower) * 4)  -- 24

--逻辑运算符
exponentNum1 = 10
exponentPower = 4

print(exponentNum1 and exponentPower) -- 4,因为第一个参数为true,所以返回4
print(exponentNum1 or exponentPower)    --10,因为第一个参数为true

exponentNum1 = false
print(exponentNum1 and exponentPower)  --false,因为第一个参数为false,所以返回false

a = 4
b = 10

print( a < b or "this statement is false")  --true,or的话第一个参数为true直接返回
print( a > b or "this statement is false")  --this statement is false,or的话第一个参数为false返回第二个参数
print( not(a + 11 < b) or "this statement is false") --true,or的话第一个参数为true直接返回

-- Catenation string
exampleCatenationString = "Hello " .. "World!" -- Hello World!
print(#exampleCatenationString) -- 12

--print(exampleCatenationString)

二、条件语句

--条件运算
if 3 > 5 then
    print("this statement is true")
elseif 20 > 15 then
    print("20 > 15")
else
    print("this statement is false")
end

--常用函数
print(type(20)) --number,类型为number类型

testVar = nil
if type(testVar) == "number" then
    print("testVar is a number")
elseif type(testVar) == "string" then
    print("testVar is a string")
else
    print(testVar)
    print("testVar is a else")
end

三、循环

print("------while loop example------")
iter = 0
while iter <= 10 do
    print(iter)
    iter = iter + 1
end

print("------for loop example------")
--等同于while循环,默认递增为1,所以不用写
for i = 0, 10 do
    print(i)
end

print("-----改变递增系数-----")
--以3为递增
for i = 0, 10, 3 do
    print(i)
end

print("-----增加退出循环条件-----")
for i = 0, 10 do
    print(i)
    if i == 5 then break end  --假如比较简单,可以直接一行
end



print("------until loop example------")
element = 0
repeat
    print(element)
    element = element + 1
until element > 10

四、基本表

t = {1, "hello", true, four = 4, five = true, six = "world"} --可以放置任何类型
print(t[2])  --hello
print(t[4])  --nil,直接打印第4个元素为nil
--以键值对的方式访问
print(t["four"]) --4
print(t.four) --4
print(t.five, t["six"]) --true  world

--sizeof表
print(#t)  --3,nil的不算在内

examT = {1, 2, 3, 4, 5, 6}
print(#examT) --6

examString = "know"
print(#examString)  --4

五、函数

(1)命名函数的两种方式.

function f()
    print("Hello")
end

g = function()
    print("Hello again")
end

f()  --推荐这种用法
g()

function println(value)
    print(value)
end
println("Arun")
println(10)

y = 911  --全局变量
function addPrint(a, b)
    x = "101010101010"
    print(x)
    y = 912
    return a + b
end

t = {addPrint(1, 2), 23}
println(t[1])
print(x)
print(y)

(2)变量的作用域

--x = 12            --打开这个变量,可以看出x变量的值的范围
function add(a, b)
    x = 10          --本地变量
    local  y = 11
    print(x)        --10
    return a + b
end

print(x)                    --nil

print(add(5,15))    --20
print(x)            --10,函数内部加local关键字,它会变成全局变量
print(y)            --nil

六、内存管理

注意内存的传值引用和传址引用

------------------
x = 10
y = x
x =20
print(x)
print(y)

--[[输出=>
20
10]]
------------------
m = {10, 20, 30}
n = m
m[2] = 40

print(m[2])
print(n[2])
--[[输出=>
40
40]]

七、闭包

function f()
    local x = 1
    return function() print(x); end
end

printHello = f()
printHello() --1
-------------------------------
function createIter()
    local i = 0
    return function() print(i); i = i + 1 end
end

iter = createIter()
iter()  --0
iter()  --1
iter()  --1

八、table面向对象实现

Player = {
    x = 0, y = 0,
    name = "",
    new = function()
        p = {}
        for k, v in pairs(Player) do
            p[k] = v
        end
        return p
    end,

    move = function(obj, x,y)
        obj.x = obj.x +x
        obj.y = obj.y +y
    end
}

p1 = Player.new()

p1.x = 10
p1.y = 20
p1.name = "Bob"

p2 = Player.new()
p2.x = 30
p2.y = 50
p2.name = "Steve"

print(p1.x, p1.y, p1.name)  --10        20      Bob
print(p2.x, p2.y, p2.name)  --30        50      Steve

p1.move(p1, 10, 10)
p2.move(p2,70,90)
print(p1.x, p1.y)   --20        30
print( p2.x, p2.y)  --100       140

九、meta表高级用法,重写原始操作符

Vector2 = {
    x = 0, y =0,
    mt = {},
    New = function()
        local vec = {}

        setmetatable(vec, Vector2.mt)

        vec.x = Vector2.x
        vec.y = Vector2.y
        vec.mt = Vector2.mt
        vec.Translate = Vector2.Translate
        return vec
    end,
    Translate = function(self, dx, dy)
        self.x = self.x + dx
        self.y = self.y + dy
    end
}
Vector2.mt.__add = function(v1, v2)
    local vec = Vector2.New()
    vec.x = v1.x + v2.x
    vec.y = v1.y + v2.y
    return vec
end

Vector2.mt.__sub = function(v1, v2)
    local vec = Vector2.New()

    vec.x = v1.x - v2.x
    vec.y = v1.y - v2.y

    return vec
end

-- __mul, __div, __mod,
Vector2.mt.__eq = function(v1, v2)
    return v1.x == v2.x and v1.y == v2.y
end
-- __lt, __le, __gt, __ge

Vector2.mt.__tostring = function(vec)
    return "(" .. vec.x .. ", " .. vec.y .. ")"
end

Vector2.mt.__metatable = "Private"

--[[Vector2.mt.__index = Vector2

Vector2.mt.__newindex = function(t, k, v)
    error("Cannot change values of Vector2 instance.")
end]]

v1 = Vector2.New()
v1.x = 10
v1.y = 20
--v1.Translate(v1, 10, 10)
--等同于
--v1:Translate(10, 10)
--print(v1.x, v1.y)       --20  30

v2 = Vector2.New()
v2.x = 30
v2.y = 40

v3 = v1 + v2
print(v3.x, v3.y)       --40    60

v4 = v1 - v2
print(v4.x, v4.y)       -- -20  -20


print(v4)               -- (-20, -20)
print(getmetatable(v4)) -- Private
print(v1 == v2)         -- false

--setmetatable(v4, nil)   --test.lua:71: cannot change a protected metatable

十、高级循环

t1 = {1, 2, 3}
t1[2] = nil
for i=1, #t1 do
    print(i, t1[i])
end
--[[1   1
2       2
3       3]]

t2 = {one = 1, two = 2, three = 3}

for k,v in pairs(t2) do   --是pairs而不是ipairs
    print(k, t2[k])
end
--[[
one     1
three   3
two     2]]


t3 = {1, 2, 3, 4, 5}
function numIter(tb, start)
    i = start
    return function()
        i = i + 1
        if tb[i - 1] then
            return i - 1, tb[i - 1]
        else
            return nil
        end
    end

end

for k,v in numIter(t3, 1) do
    print(k, v)
end
--[[
1       1
2       2
3       3
4       4
5       5]]

十一、lua内运行外部代码的三种方式

(1)test1.lua

for i = 0, 10 do
    print("hello")
end
return 100

(2)main.lua

-- dofile, loadfile load
--<1>加载执行文件第一种方式
--dofile("/Users/00arunalldata00/006_eleallproject/002ngconf/002_camel-agent-deploy/router-lua-module/aruntest/lua_learning/test1.lua")

--<2>加载执行文件第二种方式
--[[function newDoFile(filename)
    f = assert(loadfile(filename))
    return f()
end

newDoFile("./test1.lua")
print(newDoFile("./test1.lua"))  -- 100]]

--<3>加载执行文件第三种方式
--(1)load和函数调用第一种区别
f = load("print(20)")
f() -- 20

function g()
    print(20)
end
g() -- 20
--(2)load和函数调用第二种区别
x = 10
local x = 20
function f1()
    x = x + 1
    print(x)
end
f1()  -- 21

g1 = load("x = x + 1;print(x)")
g1()  -- 11

十二、

Reference:

https://www.youtube.com/playlist?list=PL0o3fqwR2CsWg_ockSMN6FActmMOJ70t_